Fin flapping in CFX

Shyam123 · August 1, 2017, 08:23

Hello everyone,

I have been working on a Project based on MantaRay and my Task is to simulate the fin flapping of the Manta and simulate the same and analyse the results.
I have created the geometry in SOLIDWORKS and the mesh in ICEM, I have imported the mesh into CFX but i am not able to find a way to move the fins.
It would be really helpful if somebody can help me in this regard.

Best regards

Shyam

ghorrocks · August 1, 2017, 19:35

This sounds like a moving mesh application. Have a look for the moving mesh tutorial examples on the ANSYS customer webpage, and read the documentation on moving mesh.

Shyam123 · August 2, 2017, 05:50

Thank you for the Response.

The method I have to follow is Immersed boundary method so it is not a Body conformal method.

Is there any way I can define the Motion and apply the immersed Body conditon in CFX.

Regards

Shyam Prithvi

ghorrocks · August 2, 2017, 06:51

You could do it with immersed solids. The advantage of this is you can have a high quality mesh and impose a very complex motion on it and have no problems with mesh folding. The disadvantage is that you cannot resolve the boundary layer with a fine mesh and you can't use inflation layers.

So if accurate resolution of the boundary layer is required then you have to use moving mesh. If not then immersed solid is OK.

On second thoughts - immersed solid is a rigid body modelling tool. The solid must be rigid, but it can translate and rotate. So you cannot model the flapping wing of a Manta Ray. You might be able to approximate a flexible body by having many small rigid bodies and moving them to approximate a flexible body - this sounds difficult to me.

I suspect you are going to have to use moving mesh.

Shyam123 · August 2, 2017, 07:02

Yes, I have divided the fin into small segments to give the movement.

Can you please let me know how to define the movement of the fin.
I have the equation and the input values to define the movement but I cannot find any tutorial as to where I have to put these to get the desired movement.

Regards

Shyam

ghorrocks · August 2, 2017, 07:10

There is no tutorial on this. I do not even know if it can be done. You are going to have to work it out yourself based on the rigid body motion stuff which is there already.

Shyam123 · August 2, 2017, 07:15

Thank you for the response.

Regards

Shyam

August 1, 2017, 08:23	Fin flapping in CFX	#1
Shyam123 New Member Join Date: Jul 2017 Posts: 8 Rep Power: 8	Hello everyone, I have been working on a Project based on MantaRay and my Task is to simulate the fin flapping of the Manta and simulate the same and analyse the results. I have created the geometry in SOLIDWORKS and the mesh in ICEM, I have imported the mesh into CFX but i am not able to find a way to move the fins. It would be really helpful if somebody can help me in this regard. Best regards Shyam

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August 1, 2017, 19:35		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	This sounds like a moving mesh application. Have a look for the moving mesh tutorial examples on the ANSYS customer webpage, and read the documentation on moving mesh.

August 2, 2017, 05:50		#3
Shyam123 New Member Join Date: Jul 2017 Posts: 8 Rep Power: 8	Thank you for the Response. The method I have to follow is Immersed boundary method so it is not a Body conformal method. Is there any way I can define the Motion and apply the immersed Body conditon in CFX. Regards Shyam Prithvi

August 2, 2017, 06:51		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You could do it with immersed solids. The advantage of this is you can have a high quality mesh and impose a very complex motion on it and have no problems with mesh folding. The disadvantage is that you cannot resolve the boundary layer with a fine mesh and you can't use inflation layers. So if accurate resolution of the boundary layer is required then you have to use moving mesh. If not then immersed solid is OK. On second thoughts - immersed solid is a rigid body modelling tool. The solid must be rigid, but it can translate and rotate. So you cannot model the flapping wing of a Manta Ray. You might be able to approximate a flexible body by having many small rigid bodies and moving them to approximate a flexible body - this sounds difficult to me. I suspect you are going to have to use moving mesh.

August 2, 2017, 07:02		#5
Shyam123 New Member Join Date: Jul 2017 Posts: 8 Rep Power: 8	Yes, I have divided the fin into small segments to give the movement. Can you please let me know how to define the movement of the fin. I have the equation and the input values to define the movement but I cannot find any tutorial as to where I have to put these to get the desired movement. Regards Shyam

August 2, 2017, 07:10		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	There is no tutorial on this. I do not even know if it can be done. You are going to have to work it out yourself based on the rigid body motion stuff which is there already.

August 2, 2017, 07:15		#7
Shyam123 New Member Join Date: Jul 2017 Posts: 8 Rep Power: 8	Thank you for the response. Regards Shyam